How to Air-Layer an old tree for Bonsai

Air-layering is a popular method for propagating trees, and it’s particularly effective for species like the Malus Royalty Crabapple and many other deciduous tree's. The process allows you to create a new tree from a mature one by encouraging roots to grow on a branch, which can then be separated and potted up. This guide will walk you through the steps to successfully air-layer an old tree for bonsai.

What You’ll Need:

• A healthy tree (ensure it’s at least 2-3 years old with healthy branches)

• Sharp pruning shears or a clean, sharp knife

• Rooting hormone (optional, but helpful)

• Sphagnum moss (highly recommended for root growth)

• Plastic wrap or clear plastic bag (to cover the air-layer site)

• Aluminum foil or cling film (to keep the moss moist)

• Twist ties or string (to secure the wrap)

• A bucket of water (to soak the sphagnum moss)

• A clean, sharp cutting tool or chainsaw (to remove the air-layer once rooted)

• Potting soil (for transplanting once the roots have formed)

Step-by-Step Guide:

1. Choose the Right Branch

The first step is to select the perfect branch on the tree for air-layering. Look for a healthy, mature branch that is about the size of a pencil at minimum and preferably near the bottom half of the tree. It should be free from pests, diseases, and significant damage.

Ideally, choose a branch that is no more than 3-4 feet (1 meter) from the ground if possible (but not allways the case I know). A branch with a little bit of curvature will help your future bonsai look natural.

2. Prepare the Branch

Using your grafting knife or a sharp blade of your choosing, make an incision on the branch to encourage root formation. There are a couple of ways to approach this:

• Ring Girdling Method: Using a sharp knife, cut a shallow ring around the branch and be sure the cut is thicker than the branch so it can not bridge over. Be careful not to cut too deeply into the branch if its pencil thin. Then, gently peel away the bark, exposing the cambium layer beneath. Scrape away the cambium all around the incision. This will prevent the flow of nutrients to the upper portion of the branch, encouraging root growth below the cut.

• Advance Method: see pictures.
  

3. Apply Rooting Hormone (Optional)

Once you’ve exposed/removed the cambium layer, it can be helpful to apply some rooting hormone. This encourages quicker root formation. If you don’t have rooting hormone, don’t worry—air layering works well without it.

If you will use it be sure to apply where you want roots to grow. Above the incision not below where you have removed the bark.

4. Wrap the Area with Moist Sphagnum Moss

Take a handful of sphagnum moss and soak it in water for about 15 minutes. After soaking, wring out any excess water, then wrap the moss around the area you want roots to grow. The moss should be dense enough to completely cover the exposed area. If you feel you have used enough moss add more for safe measures.

5. Cover the Moss with Plastic Bag

Once the moss is in place, cover it with plastic wrap or a clear plastic bag to retain moisture. You can also use aluminum foil to help keep the area insulated and prevent moisture loss. Secure both ends of the plastic wrap with twist ties or string to ensure the moss stays in place and remains moist. After this step I also like to use a black bag as an outer layer that I can easily remove for inspection with out disturbing the rest.

6. Maintain Moisture and Monitor Growth

After setting up the air-layer, it’s important to keep an eye on the moss and make sure it remains moist. Check it every couple of weeks. If the moss starts to dry out, you can gently mist it with water or rewrap the moss with fresh, damp moss.

7. Wait for Roots to Form

The root development process can take anywhere from 4-12 weeks on average but I have known some trees to take longer than a year to produce roots like the malus royalty pictured., but also alot depends on the climate, temperature, and the health of the tree. You will start to see small roots growing through the moss. Once the roots are visible through the plastic wrap, you will start to feel excited from success but I would suggest in waiting for that bag to be over flowing before removel.

8. Cut the New Tree from the Parent Plant

Once the roots are well-established and visible, use a sharp, clean cutting tool to remove the branch below the newly formed roots. Be sure to leave a couple of inches of the original branch intact, as this will help with transplanting.

You could just do what I do and use a chainsaw to remove the large branches.

9. Pot the New Tree up Bonsai

After removing the air-layered branch, carefully pot the new tree. Use a well-draining bonsai soil mix to ensure good root health. Do not trim or disturb the roots at this time. And make sure it does not move around in the pot as this will be very detrimental and could waste your last few months work and patience.

Place the tree in a shaded area for a few weeks to allow it to adjust to its new environment. Afterward, you can gradually introduce it to more sunlight.

10. Pruning and Training the Bonsai

I personally would wait at least 1 year before working on new air-layered materials, just as you would with yamadori (collected trees from the wild). Giving the tree time to recover will really improve your chances of success with a tree full of vigor and health. Working on it soon as its potted up is not ideal.

Tips for Success:

• Best Time for Air-Layering: Early spring to mid-summer is the best time to air-layer. During these warmer months, the tree is actively growing, which helps in the formation of roots. You can technically start the air-layer any time of the year but starting at the best times makes things alot easier.

• Moisture is Key: Always ensure the moss remains moist but not soaked. Too much water can cause rot, and too little can prevent root formation.

• Avoid Direct Sunlight: While the air-layer is developing, keep it out of direct sunlight to avoid drying out the moss.

• Be Patient: Root development can take time, especially for crabapple trees. Be patient and monitor the process regularly.

Conclusion:

Air-layering an old tree for bonsai is a rewarding and effective way to propagate a new tree with desirable characteristics. By following these steps, you can successfully create a new bonsai specimen from an existing tree, allowing you to enjoy this stunning species for years to come. With careful attention to detail, patience, and proper care, your new bonsai will thrive and be a beautiful addition to your collection.

If you are more of a visual learner you can watch a full video on this subject if you scroll down a little further.